Intermediate frequency independent star mixer

Abstract

An apparatus for mixing electrical signals including in combination: first signal splitting means having a radio frequency (RF) port and first, second, third and fourth signal ports, second signal splitting means having a local oscillator (LO) port and first, second, third and fourth signal ports, intermediate frequency (IF) port, and mixer element means, the mixer element means coupled to the first, second, third, and fourth signal ports of the first and second signal splitting means and coupled to the intermediate frequency port means, for mixing two of the RF, IF, and LO signals to produce the remaining signal.

What is claimed is: 
     
       1. An apparatus for mixing electrical signals including in combination: first signal splitting/combining means having a first I/O port and first, second, third and fourth signal ports, said first I/O port for coupling a first frequency signal, said first signal splitting/combining means for splitting signals from said first I/O port to said first, second, third and fourth signal ports, or for combining signals from said first, second, third and fourth signal ports to said first I/O port, or both;   second signal splitting/combining means having a second I/O port and first, second, third and fourth signal ports, said second I/O port for coupling a second frequency signal, said second signal splitting/combining means for splitting signals from said second I/O port to said first, second, third and fourth signal ports, or for combining signals from said first, second, third and fourth signal ports to said second I/O port, or both;   third I/O port means for coupling a third frequency signal; and   five port mixer element means, said five port mixer element means having first, second, third and fourth ports coupled to said first, second, fourth and third signal ports of said first signal splitting/combining means, respectively, said first, second, third and fourth ports of said five port mixer element means coupled to said first, third, fourth and second signal ports of said second signal splitting/combining means, respectively, and a fifth port of said five port mixer element means coupled to said third I/O port means, said five port mixer element means for mixing two of three signals comprising said first, second and third frequency signals to produce a remaining one of three signals comprising said first, second and third frequency signals.   
     
     
       2. Apparatus for mixing of electrical signals as claimed in claim 1, wherein said first and third signal ports of said first signal splitting/combining means provide 180° of phase shift relative to said second and fourth signal ports of said first signal splitting/combining means. 
     
     
       3. Apparatus for mixing of electrical signals as claimed in claim 1, wherein said first and third signal ports of said second signal splitting/combining means provide 180° of phase shift relative to said second and fourth signal ports of said second signal splitting/combining means. 
     
     
       4. Apparatus for mixing of electrical signals as claimed in claim 1, wherein said first and second signal splitting/combining means further comprise filters. 
     
     
       5. Apparatus for mixing of electrical signals as claimed in claim 4, wherein said filters comprise monolithic microwave electrical circuits. 
     
     
       6. Apparatus for mixing of electrical signals as claimed in claim 1, wherein said five port mixer element means comprises a star mixer element means. 
     
     
       7. Apparatus for mixing of electrical signals as claimed in claim 1, wherein said apparatus for mixing electrical signals receives as said first frequency signal a radio frequency signal and as said second frequency signal a local oscillator signal, to produce an intermediate frequency signal as said third frequency signal. 
     
     
       8. Apparatus for mixing of electrical signals as claimed in claim 1, wherein said apparatus for mixing electrical signals receives said third signal as an intermediate frequency signal and said second frequency signal as a local oscillator signal signal, to produce said third frequency signal as a radio frequency signal. 
     
     
       9. A method for mixing of a first electrical signal having at least a first frequency with a second electrical signal having at least a second frequency to form a third electrical signal having at least a third frequency, comprising the steps of: coupling said first electrical signal to a first phase shift array means having a first input port and first, second, third and fourth output ports, to provide first and third output signals differing in phase by 180° from second and fourth output signals;   coupling said second electrical signal to a second phase shift array means having a first input port and first, second, third and fourth output ports, to provide fifth and seventh output signals corresponding to said first and third output ports, respectively, differing in phase by 180° from sixth and eighth output signals corresponding to said second and fourth output ports, respectively;   supplying said first and fifth output signals from said first output ports of said first and second phase shift array means to a first port of a five port mixer element means, said second output signal from said second output port of said first phase shift array means and said seventh output signal from said third output port of said second phase shift array means to a second port of said five port mixer element means, said third output signal from said third output port of said first phase shift array means and sixth output signal from said second output port of said second phase shift array means to a third port of said five port mixer element means, said fourth and eighth output signals from said fourth output ports of said first and second phase shift array means to a fourth port of said five port mixer element means; and   mixing signals present at said first, second, third and fourth ports of said five port mixer element means, to create said third electrical signal at a fifth port of said five port mixer element means from said first electrical signal and said second electrical signal.   
     
     
       10. A method for mixing of electrical signals as claimed in claim 9, further including the step of providing first, second third and fourth matching element means coupled to each adjacent pair of said first, second, third and fourth ports of said five port mixer element means for impedance matching said five port mixer element means to said first and second phase shift array means, wherein said first matching element means is coupled between said first and second ports of said five port mixer element means, said second matching element means is coupled between said second and third ports of said five port mixer element means, said third matching element means is coupled between said third and fourth ports of said five port mixer element means and said fourth matching element means is coupled between said fourth and first ports of said five port mixer element means. 
     
     
       11. A method for mixing of electrical signals as claimed in claim 10, wherein said step of providing matching element means further includes the step of providing matching element means comprising inductors. 
     
     
       12. A method for mixing of electrical signals as claimed in claim 11, wherein said step of providing inductors further includes the step of providing inductors comprising monolithic microwave integrated elements. 
     
     
       13. A method for mixing of electrical signals as claimed in claim 10, wherein said steps of coupling further include the step of filtering said first and second electrical signals. 
     
     
       14. A method for mixing of electrical signals as claimed in claim 13, wherein said step of filtering further includes the step of filtering by means of fourth order filter circuits. 
     
     
       15. A method for mixing of electrical signals as claimed in claim 9, wherein said step of supplying further includes the step of supplying said fifth, sixth, seventh and eighth output signals of substantially equal amplitude derived from said second electrical signal via said second phase shift array means to said five port mixer element means. 
     
     
       16. A method for mixing of electrical signals as claimed in claim 9, wherein said step of supplying further includes the step of supplying said first, second, third and fourth output signals of substantially equal amplitude derived from said first electrical signal via said first phase shift array means to said five port mixer element means. 
     
     
       17. A method for mixing of electrical signals as claimed in claim 10, wherein said step of providing matching element means further includes the step of providing matching element means which effect electrical impedance matching of said first input port of said first phase shift array means without perturbing the electrical impedance of said first input port of said second phase shift array means. 
     
     
       18. A method for mixing of electrical signals as claimed in claim 10, wherein said step of providing matching element means further includes the step of providing matching element means which effect electrical impedance matching of said first input port of said second phase shift means without perturbing the electrical impedance of said first input port of said first phase shift array means. 
     
     
       19. Apparatus for mixing of a first electrical signal having at least a first frequency with a second electrical signal having at least a second frequency to form a third electrical signal having at least a third frequency, comprising: first phase shift array means having first, second, third and fourth phase shift networks; an input port means for coupling said first electrical signal; and first, second, third and fourth output ports, for providing a phase reversal from one output port pair with respect to another output port pair;   second phase shift array means having first, second, third and fourth phase shift networks; an input port means for coupling said second electrical signal; and first, second, third and fourth output ports, for providing a phase reversal from one output port pair with respect to another output port pair;   mixer element means having first, second, third and fourth input ports and a fifth output port, said first input port being connected to said first output ports of said first and second phase shift means, said second input port being connected to said second output port of said first phase shift means and to said third output port of said second phase shift means, said third input port being connected to said fourth output ports of said first and second phase shift means, said fourth input port being connected to said third output port of said first phase shift means and to said second output port of said second phase shift means, said mixer element means for providing said third electrical signal at said fifth output port; and   first, second, third and fourth matching element means, said first matching element means coupled between said first and second input ports of said mixer element means, said second matching element means coupled between said second and third input ports of said mixer element means, said third matching element means coupled between said third and fourth input ports of said mixer element means, said fourth matching element means coupled between said fourth and first input ports of said mixer element means, for providing impedance matching of said mixer element means and said first and second phase shift array means.   
     
     
       20. Apparatus for mixing of electrical signals as claimed in claim 19, wherein said first, second, third, and fourth matching element means comprise inductors. 
     
     
       21. Apparatus for mixing of electrical signals as claimed in claim 19, wherein said first and second phase shift array means comprise lumped element monolithic microwave circuits. 
     
     
       22. Apparatus for mixing of electrical signals as claimed in claim 20, wherein said inductors comprise monolithic microwave electronic elements. 
     
     
       23. Apparatus for mixing of electrical signals as claimed in claim 19, wherein said first and second phase shift array means comprise fourth order filter circuits. 
     
     
       24. Apparatus for mixing of electrical signals as claimed in claim 19, wherein said first and third matching element means affect matching of said first phase shift array means without affecting electrical matching of said second phase shift array means. 
     
     
       25. Apparatus for mixing of electrical signals as claimed in claim 19, wherein said second and fourth matching element means affect matching of said second phase shift array means without affecting electrical matching of said first phase shift array means.